Woodell



July 16, 1963 R. WOODELL 3,097,414

CRIMPABLE FIBERS OF REGENERATED CELLULOSE Filed Oct. 50, 1958 2Sheets-Sheet 1 INVENTOR RUDOL PH WOODELL ATTORNEY July 16, 1963 R.WOODELL 3,097,414

CRIMPABLE FIBERS OF REGENERATED CELLULOSE Filed Oct. 50, 1958 2Sheets-Sheet 2 INVENTOR R UDOL PH WOODELL ATTORNEY United States Patent3,097,414 CRIMPABLE FIRE 0F REGENERATED CELLULOSE Rudolph Woodell,Kinston, N.C., assignor, by mesne assignments, to Beaunit Corporation, acorporation of New York Filed Oct. 30, 1958, Ser. No. 770,656 2 Claims.(Cl. 28-452) This invention relates to novel and useful crimpable rayonfibers, and a process for their production.

The production of crimpable filaments by extruding two or more viscoses,having different shrinkage potentials, through the same spinneret holeis known. While these multi-component filaments are superior in certainrespects to single component filaments, i.e., in ease of crimping andcrimp retention, they are deficient in other characteristics such asabrasion resistance and resistance to soiling.

It is an object of this invention to provide a new and useful crimpableviscose rayon fiber.

Another object is to provide a crimpable fiber which crimps readily inwater and has excellent crimp retention, abrasion resistance andresistance to soiling.

Another object is to provide a process for producing such fibers.

These and other objects will become apparent in the course of thefollowing specification and claims.

In accordance with the present invention a viscose rayon fiber isprovided consisting of two components, a first component having atransverse cross-section characterized by a smooth substantiallyuncrenulated contour and a thick, preferably at least 80% skin, and asecond component having a transverse cross-section characterized by asmooth contour and a core surrounded by a skin, the percentage of skinin the second component being substantially less than the percentage ofskin in the first component and the two components being fused togetheralong their entire length to form a single coherent fiber. Preferablythe second component has at least about 20% less skin than the firstcomponent. It is also preferable that each component is substantiallyoval in shape and the two components are joined in such manner thattheir long axes, if extended to intercept one another, form a T.

The process for forming the yarn described above comprises preparing twoviscoses, A and B, adding to viscose A a small amount of cyclohexylamineas a coagulation modifier, extruding the two viscoses simultaneously inside-by-side relationship through the same spinneret hole into acoagulating and regenerating bath containing from about 6.5 to about 10%sulfuric acid, from about 12 to about 23% sodium sulfate, at least aboutzinc sulfate, and a small amount of cyclohexylamine, viscose A having asalt index of at least 5, viscose B having a salt index of at least 2,and stretching the yarn. Preferably the salt index of viscose A is atleast 3 units higher than that of viscose B.

FIGURE 1 is an exploded view of a device useful in the extrusion of theyarn of the present invention.

FIGURE 2 is a rear view of the equalizer and separator section of thedevice illustrated in FIGURE 1.

FIGURES 3 and 4 are illustrations of the yarn cross sections produced asdescribed in Examples I and III respectively.

The following examples are cited to illustrate the invention. They arenot intended to limit it in any manner. The apparatus used in eachexample is that shown in FIGURE 1. The yarn produced is extruded throughthe orifices 1 of spinneret plate 2, the said plate being positionedagainst the equalizer and separator section 3 by means of internallythreaded spinneret adapter 4,

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flange 5 of the spinneret plate being held against the front face of theequalizer and separator section by the face 6 of the said spinneretadapter. Concentric cylindrical separator rings 7 extend through theequalizer and separator section, the said rings being supported by thepressure equalizer plate 8 (shown in FIGURE 2) which holds them in fixedrelation to the circumference of the said equalizer and separatorsection. The concentric cylindrical separator rings are beveled to asharp edge which extends beyond the engaging threads of the equalizerand separator section to such an extent that when the spinneret plate 2is positioned as previously described the sharp edges of the separatorrings are immediately adjacent to the back face of spinneret plate 2 andso arranged that each edge bisects each orifice in a particular ring ofthe said orifices. Pressure equalizer plate 8 (FIGURE 2) containsconcentrically arranged holes 9 fitting into spaces between theconcentric separator rings previously described and act to control thepressure of, and prevent pressure surges in, viscose delivered to thespinneret plate. Pressure equalizer plate 8 fits by threaded means ontoa concentric conduit 10 which contains openings 11 through which variousviscoses may be pressure fed to the system.

Example I Two viscoses, A and B are prepared in the conventional manner.Viscose A containing 8% recoverable cellulose, and 7% alkali, calculatedas sodium hydroxide, is prepared from cotton linters pulp using 30%carbon disulfide based on the air dry weight of the pulp. Sulficientcyclohexylamine is added to the viscose during the mixing operation togive a concentration of 0.15% by weight. Viscose B is prepared in anidentical fashion except that the cyclohexylamine is omitted. Viscose Ais ripened to a salt index of 8.3 and a viscosity of 40 poises whileviscose B is ripened to a salt index of 2.7 and a viscosity of 45poises. Viscoses A and B are then supplied by means of separate gearpumps, each having a delivery of 158 gpm to alternate openings of aconcentric conduit as illustrated in FIGURE 1. In this manner the twoviscoses are extruded through each of the spinneret holes inside-by-side relationship by means of the separator rings and pressureequalizer assembly. A spinneret of 1 inches diameter having 250 holes of0.008 inch diameter arranged in three concentric circles, the diameterof the circles being /2 inch, 1 inch, and 1% inches respectively isemployed.

The viscoses are extruded into a coagulating and regenerating bathcontaining 9.0% sulfuric acid, 17.5% sodium sulfate, 9.5% zinc sulfate,and 0.1% cyclohexylamine, the temperature of the bath being 60 C. Thefilaments are lead for a distance of 31 inches through the bath, thenover a Y convergence guide and for a further distance of 119 inches, theyarn being confined in the bath by means of a series of roller guides.By means of tension type roller guides, the yarn is stretched 29%between the spinneret and wind-up based on jet velocity and Wind-upspeed. The yarn is led upwardly from the coagulating bath to and arounda power-driven feed wheel, then downwardly to a centrifugal spinningbucket where it is Wound into a cake in the conventional manner. Theperipheral speed of the feed wheel is 50 y.p.m. The yarn is purified anddried in the conventional manner. Thereafter it is passed through aslashing machine where it is treated with a hot aqueous finish solution,stretched 12% and then dried under tension and wound onto pirns.

The yarn filaments are examined by cutting thin transversecross-sections in the conventional manner, dyeing these cross sectionsand examining them under high magnification. The cross sections are dyedfollowing the method described by Morehead and Sisson, Textile ResearchJournal, 15, 4445 (1945) except that pontamine yellow dye is substitutedfor calcomine yellow dye. Measurements made on ten filamentcross'sections selected at random give an average of 90% skin for oneportion of the cross section while the other portion had an average of57% skin. Both parts of the cross section are substantially uncrenulatedand shaped as illustrated in FIG- URE 3. The filament denier of thefinished yarn is 22 denier per filament. When the yarn is placed inwater at 90 to 100 C. in a relaxed state followed by drying in a relaxedstate, it is found that the yarn has an excellent crimp. On repeatedwetting and drying of the yarn, the crimp is retained substantially tothe same extent as found in the original crimped yarn. When the yarn isfabricated into a tufted carpet in the conventional manner, the carpetis found to have superior abrasion resistance and resistance to soilingas compared to similar carpets fabricated from conventional crimpedyarns.

Example 11 Two viscoses, C and D, are prepared, viscose C being preparedin the same manner as viscose IA of Example I and viscose D beingprepared in the same manner as viscose B of Example I. Viscose C isripened to a salt index of 8.0 and a viscosity of 81 poises whileviscose D is ripened to a salt index of 2.7 and a viscosity of 95poises. The two viscoses are then supplied to a common spinneret bymeans of separate gear pumps, each having a delivery of 58.1 g.p.m. Theviscoses are extruded through a spinneret of 1 inch diameter, having 120holes of 0.008 inch diameter arranged in two concentric circles, thediameter of the circles being inch and 4 inch respectively. The twoviscoses are extruded through each of the spinneret holes as describedin Example I into the coagulating bath of Example I. The filaments areled for a distance of 44 inches through the bath, then over a Yconvergence guide and for a further distance of 170 inches, the yarnbeing confined in the bath by means of a series of roller guides. Theyarn is then led upwardly from the coagulating bath to a first powerdriven 'feed wheel, then to a second power driven feed wheel rotating atthe same speed as the first but having a sufficiently larger diametertostretch the yarn 46%. A hot aqueous solution containing 2.0% sulfuricacid, 3.9% sodium sulfate and 2.1% Zinc sulfate at a temperature of 93C. is jetted onto each of the feed wheels at the top. By means of asnubbe-r roller in combination with each feed wheel, the yarn is given asufiicient number of passes around the feed wheel to give the yarn atravel of 160 inches in this area. The yarn is led from the second feedWheel, which has a peripheral speed of 50 y.p.m., downwardly to 13.centrifugal spinning bucket where it is wound into a cake in theconventional manner. The yarn is purified and dried in the conventionalmanner. Thereafter it is passed through a slashing machine where it isfirst passed through a hot aqueous finish solution, stretched 12% andthen dried under tension and wound onto pirns. The yarn denier is 2400.

When the yarn is relaxed in a hot water bath at 90 to 100 C. and thendried in a relaxed state, it has an excellent crimp. When the yarn isfabricated into a tufted carpet, the results are substantially the sameas found in Example I with filament cross sections substantially thesame as in Example I. The filament denier of the finished yarn is denierper filament.

Example III Viscoses are prepared and spun and the yarn purified exactlyas described in Example II except that each viscose is extruded at arate of 72.8 g.p.m. to give a yarn of denier per filament. Onexamination of the filament cross sections as described in Example I,the skin in one portion of the cross section is found to amount to 77%of the total area on the average while in the other section.

portion of the cross section 44% of the total area is skin. The twoportions of the cross section are substantially uncrenulated and theshape of the cross sections are substantially as shown in FIGURE 4.

When the yarn is relaxed in hot water at -100 C. and then dried in arelaxed state, it has an excellent crimp. When the yarn is fabricatedinto tufted carpets, the results are substantially the same as found inExample I.

The foregoing examples illustrate the advantages of the novel and usefulcrimped fibers of the present invention. By providing a filament havinga relatively thick skin as compared to the crimped yarns of the priorart, the strength and abrasion resistance of the fiber is improved,while the smooth substantially uncrenulated contour leads to improvedresistance to soiling. In addition, the unique shape of the crosssection provides relatively high bulk.

The essential factor in producing the fibers of this invention is theextrusion of two viscoses, one containing cyclohexylamine modifier andthe other containing no modifier, into a coagulating and regeneratingbath containing a small amount of cyclohexylarnine modifier and asubstantial concentration of zinc sulfate. The combination of modifierin the viscose and in the bath gives one component of the filament aheavy skin and a noncrenulated contour while the other component has amuch thinner skin but still has a substantially non-crenulated contourdue to the action of the modifier in the bath. The zinc salt in the bathis required since the coagulation modifier is not effective in itsabsence.

The amount of cyclohexylamine required in the viscose will varydepending upon the viscose composition, the coagulating bath compositionand other factors. However, in general it is desirable to have at least0.05% present. Too much modifier in the viscose should be avoided forreasons of economy and to avoid spinning difficulties. For optimumresults, the amount of modifier in the viscose should be adjusted to thelevel required to give from about 90 to about skin in the cross This canusually be accomplished by using concentrations in the range of fromabout 0.1 to about 0.25%, although under some conditions it may bedesirable to use larger amounts in the range of from about 0.5 to about1.0%.

The minimum amount of cyclohexylamine modifier in the coagulation bathshould be at least about 0.05% and the amount used should be regulatedin relation to the amount used in the viscose so that the skin thicknessof the filament component formed from the unmodified viscose issubstantially less than the skin thickness of the filament componentformed from the modified viscose. The amount required for this purposewill vary depending on the composition of the coagulating bath, theamount of modifier used in the viscose and other conditions butordinarily will fall in the range of from about 0.05 to about 0.25%. Theregulation of the modifier in the bath is easily accomplished by oneskilled in the art. Since the cyclohexylamine added to the viscose isleached from the spinning filaments into the bath, it is usually notnecessary to add the material directly to the bath. In some cases,however, it may be desirable to remove part of the cyclohexylamine fromthe bath in order to avoid unduly high concentrations. This may beconveniently accomplished by carbon adsorption as described in US.2,787,618 or by other suitable methods.

The composition of the viscoses used in the process of this invention isnot critical. V-iscoses produced with from about 27 to about 43% carbondisulfide based on the dry weight of the pulp used are satisfactory. Theviscose may contain from about 5.5 to about 9.5% recoverable celluloseand from about 4.0 to about 8.0% alkali calculated as'sodium hydroxide.The ripeness or maturity of the viscose at spinning may vary from about5 to about 15 units as measured by the salt index method for the viscosecontaining the cyclohexylamine modifier and from about 2 to about 15salt index units for the other viscose. It is preferable, although notessential, that the viscose containing ithfi cyclohexylamine modifierhave -a salt index at spinning about 3.0 units higher than the otherviscose.

Coagulating and regenerating baths suitable for use in the presentinvention may contain from about 6.5 to about sulfuric acid, from about12 to about 23% sodium sulfate and at least about 3% zinc sulfate inaddition to the cyclohexylamine modifier. Other metal salts which maysupplement the action of the zinc sulfate may be added if desired. Theacidity of the bath should be regulated to as low a level as iscommensurate With satisfactory spinning.

The yarn should be stretched at least about 40% While passing throughthe bath. Where a hot secondary bath is used, the stretch may beconcentnated in this bath or it may be divided between the two baths asmay be desired.

After the yarn leaves the bath, it is wound into a cake in a centrifugalspinning bucket or Wound on a bobbin and thereafter purified and driedin the conventional manner.

Afler purification, the yarn is preferably given additional stretchafter thorough wetting and is then dried in the stretched condition. Thestretching is conveniently applied by passing the yarn through aslashing machine of the type used in the production of tire cord yarn.If the customary aqueous finish is applied to the yarn, the yarn isWetted with this before stretching.

The yarn crimps readily when allowed to relax in hot water followed bydrying in a relaxed state. Instead of water, various aqueous solutionsas are well known in the art may be used in the crimping operation.

While the process of this invention is suitable for producing low denierper filament yarns, it is particularly advantageous in the production ofhigh denier per filament, i.e. above 10 d.p.f., Water crimpable yarns.

The fibers of this invention may be used wherever rayon fibers arecustomarily employed. However, they are particularly suitable for theproduction of tufted carpets and cut pile fabrics.

Many modifications of the invention described herein will be apparent tothose skilled in the art from a reading of the above without a departurefrom the inventive concepts.

What is claimed is:

1. A regenerated cellulose fiber consisting essentially of a pair ofsubstantially oval cross section components fused together along theirentire lengths so that the long axes of said oval cross sections form aT when extended to the point of interception, each of said componentshaving a smooth substantially uncrenulated contour, and comprising acore completely surrounded by a thick skin, one of said componentshaving at least 20% more skin by cross sectional area than the other.

2. A regenerated cellulose fiber as defined in claim 1 wherein one ofsaid components has at least skin by cross sectional area.

References Cited in the file of this patent UNITED STATES PATENTS1,944,378 Thenoz Jan. 23, 1934 2,234,763 Hoelkeskamp Mar. 11, 19412,310,785 Herrmann Feb. 9, 1943 2,337,969 Bugge Dec. 28, 1943 2,439,814Sisson Apr. 20, 1948 2,517,694 Merion et a1. Aug. 8, 1950 2,535,044 CoxDec. 26, 1950 2,535,045 Cox Dec. 26, 1950 2,572,217 Thurmond Oct. 23,1951 2,572,936 Kulp Oct. 30, 1951 2,674,025 Ladisch Apr. 6, 1958 FOREIGNPATENTS 514,638 Great Britain Nov. 14, 1939 51,307 Netherlands Oct. 15,1941

1. A REGENERATED CELLULOSE FIBER CONSISTING ESSENTIALLY OF A PAIR OFSUBSTANTIALLY OVAL CROSS SECTION COMPONENTS FUSED TOGETHER ALONG THEIRENTIRE LENGTHS SO THAT THE LONG AXES OF SAID OVAL CROSS SECTIONS FORM AT WHEN EXTENDED